As one of the methods of mass-producing vehicle parts requiring high-strength, a hot press forming technique or a die quenching technique is employed. The die quenching technique is a technique in which a steel plate is heated to about 900° C., and the steel plate is thereafter rapidly cooled simultaneously with press forming, to quench a formed product. Further, for the heating of a steel plate, conventionally, a continuous heating furnace installed separately from the press forming apparatus is generally used.
As such a heating furnace, a hot press forming system disclosed in Patent Document 1 employs a radiation heating machine separately installed in the preceding stage of its hot press forming apparatus. In a hot press forming apparatus disclosed in Patent Document 2, such a heating furnace is separately installed in the preceding stage of the hot press forming apparatus, and heated blanks are robotically conveyed between its heating furnace and the hot press forming apparatus.
Further, additionally, in Patent Document 3, there is disclosed a hot press forming method for metal plate comprising the successive steps of “respectively attaching electrodes to one or more places of the both ends of a metal plate inside a metal die or in the vicinity of the die outside the metal die, applying an electric current between the electrodes to heat the metal plate to a predetermined working temperature by Joule heat, and performing hot press forming”.
In Patent Document 4, there is disclosed a carrier apparatus for plate material for press in which “heating means for heating a portion corresponding to a formed portion of the plate material for press is provided to a conveyor hand that conveys a plate material for press to a press die for press working”.
Patent Document 1: Japanese Patent Kokai Publication No. JP-P2006-289425A
Patent Document 2: Japanese Patent Kokai Publication No. JP-P2006-130513A
Patent Document 3: Japanese Patent Kokai Publication No. JP-P2002-18531A
Patent Document 4: Japanese Utility Model Kokai Publication No. JP-U-61-127832